Jiunn-Shyang Chiou

Shaking-table tests on plane-strain geosynthetic-reinforced model slopes using stepwise intensified sinusoidal pulse loads with specific frequencies were conducted to investigate the influence of peak ground accelerations, wave frequencies and plastic slope displacements on the horizontal acceleration response of the slope. A comparative study on the crest response behavior suggested that the tests using pulse loads give useful insights into the dynamic behavior of soil structures subjected to earthquake loads. Test results indicate that both the horizontal acceleration response at the crest and the lateral slope displacement are influenced by the horizontal peak ground acceleration, the wave frequency, and the cumulative permanent displacement of the slope. Amplification factors at the crest of the slope are functions of input wave frequencies; they decrease exponentially with increasing input horizontal peak ground acceleration. Transitions from an amplification state to a de-amplification state at the slope crest occur at certain levels of input ground accelerations, which are associated with the development of major slip planes in the slope mass (or with noticeable slope displacement). It was found that a ratio between the plastic slope displacement and the total slope height (D_max/H_t) of the order of 0.42–5.9 × 10⁻² is relevant to this amplification–deamplification transition. A practical implication of these observations is that the resonance acceleration of the slope is a major factor that needs to be considered in seismic stability analyses of reinforced slopes with a small plastic slope displacement of D_max/H_t ≈ 2.5 × 10⁻³; it does not need to be considered in the seismic stability evaluation for reinforced slopes with plastic slope displacements of D_max/H_t = 5.0–5.9 × 10⁻².

The capacity of a pile-soil system can be obtained by pushover analysis using the beam-on-nonlinear-Winkler foundation model. When the pile section enters the plastic state, the plastic hinge method is usually adopted to model its postyielding flexural behavior. The propagation of the plastic zone in a pile can be traced using a series of plastic hinges distributed along the pile that is embedded in the soil. This study proposes a proper model for arranging the distributed plastic hinges along the depths of the pile that are prone to yielding. A modified definition of plastic curvature is proposed herein in order to correctly simulate the nonlinear flexural behavior of a pile. Examples are presented to show the effectiveness of the proposed model.